Very consistent pressure, temperature, and volume--the essentials.  Pressure and temperature gages so you know what's going on.  Push-button programming of volume and temperature.  Lots of steam and a great tip design. Separate boiler can fill 1-liter presspot with hot water. Quiet pump. Programmable on/off timer.  I like having water and drain plumbed in, but the new Mini Vivaldi II is available for those who don't want to deal w the plumbing.

I'm gonna have to be super picky to add anything here:  ok, how about sometimes when the water fills there's a slight rattle, but when I nudge the machine on my counter it stops.  This probably has more to do with the fact that I have a tiled countertop, where the tiles are not all 100% level so each foot of the machine might not be at the same level.

This is my first espresso machine, and it will probably be my last.  I did a huge amount of research before I selected the Vivaldi II.  I originally wanted to spend <$1000, but the more I read, the more I realized that I didn't want to spend my time listening to a noisy machine or spending time filling & draining, temperature surfing or hooking up other things to monitor pressure and temperature.  I do that kind of stuff enough at my job as an engineer.  I also realized I wanted two boilers, which has worked out really well.  I make a lot of tea too and the boiler temperature is perfect for tea or presspot coffee.  4 months and no problems.  I'm crossing my fingers that it will stay that way for a long time.

Also, two big thumbs up to Chris at ChrisCoffee.  I bought my machine, grinder (Mazzer Mini Doserless B), and some Bumper accessories from Chris.  Everything arrived ahead of schedule & in perfect working order.  I ordered a few other accessories from some other places, and I have to say that between backorders, and other random mistakes made by the others, ChrisCoffee stands out above the rest.